There are many instances when it is desirable to leave a key proximate to the lock which it locks, yet to place the key in a circumstance such that it cannot be used by unauthorized personnel. An especially pertinent example arises in connection with automobile parking lots. Especially in lots with very large capacities, the tagging of ignition keys and their removal from the associated vehicle is not only time consuming, but also presents a substantial logistic and clerical task. The ideal situation would be one where the parking lot attendants are able to leave keys within the vehicle, yet at the same time placing the keys in a condition such that they cannot be employed by unauthorized personnel.
Typical of further environments where such need arises is the practice of real estate brokers leaving keys on the doors of houses which are for rent or sale in a locked box wherein a key is placed totally inside the box. In this situation, an authorized real estate broker can unlock the box and gain access to the key through the use of a master key so that the locked key can be used to open a door.
Various attempts have been made in the prior art to provide various apparatus which will be satisfactory for use in the above-described situations. Typical of these prior art apparatus are those disclosed in U.S. Pat. Nos. 3,636,742 issued to G. B. Ranay on Jan. 25, 1972; 3,695,067 issued to R. D. Bays on Oct. 3, 1972; 3,712,091 issued to R. J. Parent on Jan. 23, 1973; 3,742,741 issued to L. L. Cahan on July 3, 1973; and 3,744,281 issued to R. F. Logue et al on July 10, 1973. Each of these apparatus provide a means for suspending a locked box from a suitable supporting surface and means for placing a key totally inside the locked box such that the locked box can be locked by a master key and access to the locked key can be precluded. The locked boxes are openable with a master key presumably only available to authorized personnel.
Unfortunately, all of the above apparatus suffer from at least two shortcomings. First of all, it is not known whether or not a key is disposed inside one of these locked boxes unless the locked box is actually opened. This is more than an inconvenience since considerable time can be lost in determining whether or not a key is available as a result of having to open a plurality of boxes. A second shortcoming is that any of these devices can be battered or broken open without any substantial risk of damaging the key disposed therein. As a result, unauthorized personnel can essentially strong arm the locked boxes open and be presented with a perfectly usable key to the total frustration of the intended purpose of these devices.
In U.S. Pat. No. 4,090,380 to Bianco there is disclosed another device which has recently come into use in parking lots which utilizes a cylindrical body having a transverse slot into which the working portion of an ignition key may be inserted. Jaws above and below the slot are then clamped against the key portion by advancing one of the jaws axially in the body. This is effected by means of a specially shaped wrench which engages a member threadingly received into the cylinder. Such member in turn drives the one jaw toward the opposed jaw and intervening key. While this type of device has received a degree of acceptance, it suffers from the serious deficiency that a make-shift tool may be readily used to substitute for the aforementioned wrench, thereby circumventing the safeguard presumably provided by the device.
While safeguards can be provided with protective key-retaining devices which can only be opened by authorized personnel having keys, either individual or masters which are specially made for the locks used with the device, it would be particularly advantageous if such keys, and particularly those which serve as a master capable of unlocking a large number of such devices, could not itself be readily duplicated in an unauthorized manner. It is known that locks generally commercially available use keys which can be readily duplicated from standard blanks. Thus, the use of a nonstandard lock which is simple in construction, yet sturdy enough to be effective, would be a highly desirable adjunct to any protective key-retaining device.
Heretofore, a variety of different locks which require special keys have been suggested such as, for example, disclosed in U.S. Pat. No. 208,863 to Taylor, U.S. Pat. No. 704,655 to Morgan, U.S. Pat. No. 1,100,412 to Pantazi and U.S. Pat. No. 1,300,983 to Luckey. However, none of these locks disclose apparatus such as a protective key-retaining device or suggest features of construction that would be applicable for such use.